Don't do the rollback in #commit

The caller needs to have knowledge of the rollback either way, so do it
all in the caller (#transaction)

activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb

@@ -203,7 +203,7 @@ module ActiveRecord
           begin
             @transaction = @transaction.commit
           rescue Exception
-            @transaction = @transaction.parent
+            @transaction = @transaction.rollback
             raise
           end
         end

activerecord/lib/active_record/connection_adapters/abstract/transaction.rb

@@ -84,23 +84,12 @@ module ActiveRecord
         def commit
           @finishing = true
 
-          begin
-            if parent.open?
-              connection.release_savepoint
-              records.each { |r| parent.add_record(r) }
-            else
-              connection.commit_db_transaction
-              commit_records
-            end
-          rescue Exception
-            if parent.open?
-              connection.rollback_to_savepoint
-            else
-              connection.rollback_db_transaction
-            end
-
-            rollback_records
-            raise
+          if parent.open?
+            connection.release_savepoint
+            records.each { |r| parent.add_record(r) }
+          else
+            connection.commit_db_transaction
+            commit_records
           end
 
           parent